Home Shop Machining/Machining Operations/Turning Between Centers
Turning Between Centers is Easy and Useful[edit | edit source]
Many new Home Shop Machinists avoid turning between centers, preferring to chuck everything in a 3-jaw instead. This is a mistake. Not only is it easy to turn between centers, it solves a lot of problems. Most notably, it allows a part to be swapped end-for-end on the lathe so that both sides of a feature can be cut true to each other.
To start, either the part itself needs to have center holes drilled on each end or the part needs a through hole that fits over a mandrel. Next, there needs to be a way to drive the part as, by design, there's very little friction between a center and a center hole. Some sort of dog needs to be clamped to the part or the mandrel and that dog needs to be pushed in a circle by the lathe. That can be as simple as the dog going through a hole in a face plate, being pushed by the side of a chuck jaw, or even a bolt in the face plate.
Drilling a center hole in a part or new mandrel involves using an appropriately sized center drill. If the part can fit through the spindle bore of the lathe then it's easy. Simply chuck and center drill. If not, then place a heavy center-punch mark at either end of the work, fit a center drill in the tailstock, and fix the headstock end in one of two possible ways: Either chuck that end of the work or fit the dog on the end and then use the center-punch mark over a center. As the other end, fit the tip of the center drill in the other center-punch mark. Set the lathe on its slowest speed. While constantly maintaining pressure with the tailstock feed wheel, turn the lathe on for a few revolutions as the center drill feeds in. It is important to feed the tailstock as this happens. Stop the lathe. Reverse the work end for end in the lathe and repeat to drill the other end. The work now has both ends center-drilled.
Safety Tip[edit | edit source]
Note the yellow paint on the lathe dog ends as well as the bolt in the faceplate. Notice the yellow streak where showing work turning between centers. When something lumpy is spinning in a lathe, the lumpy bits tend to disappear as your eye ends up seeing the average. This can be very bad for fingers. If you paint those bits yellow, they will appear as yellow streaks that you will hopefully notice and not stick your fingers in the way of.